Spellsword

This is a re-work of the 5e official eldritch knight archetype. I really like the idea behind it, it's just that the eldritch knight has so many conflicting abilities that you only ever use less than half of the abilities given to you. It's a very good idea executed in very poor manner.

The 3rd level ability does very little for you. You can call your weapon to you, but you also can't be disarmed so the first ability will never get used. You could use a thrown weapon, but this doesn't make much sense. You have cantrips, so why would you take a melee weapon with poor damage in exchange for range?

The 7th level ability is similarly useless. You can cast a cantrip and make a melee attack as a bonus action. I really like the idea behind this ability, but it just doesn't hold up to the other abilities you have at that level. You could use your new 2nd level spell slots to cast flaming sphere, use action surge to make melee attacks for the first turn, and then make both of your melee attacks and use your bonus action to attack with your flaming sphere. If you're worried about losing concentration, don't be. You have proficiency in constitution saving throws, which includes concentration saves. You can also take the war caster feat to get advantage on the roll. Using your 7th level ability becomes obsolete at 11th level when you get a third attack as well.

The 10th and 15th level abilities are pretty good, so I'll keep those, with a few tweaks.

The 18th level ability is an upgrade to the 7th level ability that you've probably forgotten about by then, limiting the number of people likely to use it, even though you could use it to give a creature disadvantage on its saves for your spells before dropping a fireball on it. The 18th level ability is much better than its 7th level counterpart, but because most people have written off its predecessor, they might not give it a chance.

The way I see it, the base fighter class abilities compete with the eldritch knight abilities, which compete with themselves for prominence. I'm going to try and straighten things out a bit.

There are three different ways you can take this class: making melee attacks and casting a cantrip; making melee attacks and using a long-term concentration spell, like flaming sphere, enlarge/reduce, or magic weapon; or heavy spellcasting lightly supported with melee combat. I'm going to be focusing on combining melee attacks with casting cantrips here, going so far as to remove the spellcasting feature.

That's right, I'm going to try and make a better spellcasting fighter without ever giving him spellcasting.

Spell Slinging

When you reach 3rd level, you augment your martial prowess with the ability to cast spells. See chapter 10 for the general rules of spellcasting and chapter 11 for the wizard spell list.

Cantrips. You learn three cantrips: shocking grasp and two other cantrips of your choice from the wizard spell list. You learn another wizard cantrip of your choice at 10th level. In addition, when you take the attack action, you can cast a cantrip instead of one of your attacks. 

Empowered Cantrips

Beginning at 7th level, you can add your Intelligence modifier to the damage roll of any cantrip you cast. In addition,  your damaging cantrips affect even creatures that avoid the brunt of the effect. When a creature succeeds on a saving throw against your cantrip, the creature takes half the cantrip’s damage (if any) but suffers no additional effect from the cantrip.

Arcane Charge

At 10th level, you gain the ability to teleport up to 30 feet to an unoccupied space you can see when you use your Action Surge. You can teleport before or after the additional action.

Eldritch Strike

At 15th level, you learn how to make your weapon strikes undercut a creature’s resistance to your spells. When you take the attack action, choose one creature within 5 ft. of you that you hit with a melee weapon attack. If you choose to cast a cantrip against that creature on this turn, being within 5 feet of it doesn’t impose disadvantage on your ranged spell attack rolls against it until the beginning of your next turn. In addition, this creature has disadvantage on the next saving throw it makes against a spell you cast before the beginning of your next turn.

Elemental Surge

At 18th level, you have become so used to mustering up magical energy from yourself to cast your cantrips, you have learned how to continuously channel powerful elemental energy through your body instead of expelling this energy in a discrete casting of a spell. You can use a bonus action to enter a state of surging elemental magic. While in this state, you gain the following effects for one minute:

• You cannot cast spells or concentrate on them.
• You can add damage equal to 1d8 + your intelligence modifier to each of your melee weapon attacks. This extra damage is your choice of acid, cold, fire, lightning, poison, or thunder damage for each attack. For example, you could choose to deal bonus fire damage for one attack, and deal bonus lightning damage for another. 
• You gain temporary hit points equal to your fighter level + your intelligence modifier.
• You shed bright light in a 10-foot radius and dim light for an additional 10 feet after that.

You cannot use this ability again until after you have completed a long rest.